The most recent findings looked at how children's age altered the effect of parents separating.

For the very youngest children, the impact was significantly less than if the split happened later in childhood, from about the age of seven upwards.

The children in the Millennium Cohort Study are assessed every year for basic skills such as numeracy and literacy.

On both the basic education skills and the outcomes, children in single parents appear to be worse.

"We measure their wellbeing levels, of depressive symptoms, of how they're feeling, their levels of anxiety and so on. And we tend to see they're also doing worse - also on that dimension," said lead researcher Prof Emla Fitzsimons, from the Institute of Education.

The difference appears to be the greatest among teenage girls:

Of girls in a family with two parents in a stable relationship, 22% had high levels of depressive symptoms

For girls living with a single parent, this rose to 27%

But how sure can researchers be, given the many financial challenges a single parent household faces?

Prof Fitzsimons said: "There is still a difference between the outcomes of children born to single-parent households, versus married or cohabiting, even when you taken into account they tend to be from poorer homes."

The academics say these are average findings across large populations, not a judgement on any individual parents.

Neither Prof McLanahan nor Prof Fitzsimons think their research should change the complex decisions individuals make about how to raise their children.

But they are asking questions of wider society about what could be done to provide more support to parents taking on the difficult job of bringing up children on their own.